Refer to figure.
Note: This question is quite similar to Q828697 and Q829865. One important difference is that this question states that the fenestron helicopter is equipped with a relatively large vertical fin. Unfortunately, we have received various feedback regarding the question text and contradicting feedback regarding the correct answer of these questions. Further feedback would be appreciated.

In general, for a clockwise helicopter, the horizontal tail rotor thrust is to the left, to counteract the torque effect.

The Fenestron, or Shrouded Tail Rotor, is a tail rotor configuration, where the tail rotor blades are much less exposed to the confused airflow from the main rotor downwash and disturbances from the fuselage. It is a high speed, variable pitch ducted fan mounted in a cambered fin.

The shape of the duct and the cambered fin is significant. The shape of the duct increases the thrust beyond what would be expected from an exposed fan because of a phenomenon known as Coanda Effect, which accelerates the airflow entering the duct.

The cambered fin also produces aerodynamic force in forward flight, providing an anti-torque sideways thrust. This reduces the power requirement of the fan and its contribution can be as much as 50% of the required anti-torque force. At higher speeds, a large vertical fin will be acting to off-load the fenestron, like a wing in its side.

This means that for a helicopter with a clockwise rotating main rotor, the Pilot must push the left pedal to give the tail rotor blades a negative pitch angle (to minimise the tail rotor pitch angle) in order to trim the helicopter in high-speed forward flight.

In hover, the Pilot should apply right pedal (positive pitch angle) to trim the helicopter and maintain heading, preventing the helicopter spinning counterclockwise.